Assembling Homometallic Sb₆ and Heterometallic Ti₄Sb₂ Oxo Clusters

Isolation and structural characterization of novel organoantimony­(V)-based oxo clusters are reported. (RSb)₄(OH)₄(t-BuPO₃)₆ and (RSb)₂(O)­(t-BuPO₃H)₆ independently in the presence of pyridine under solvothermal conditions afford the hexanuclear organoantimonate clusters [(RSb)₆(μ₃-O)₂(μ₂-O)₆(t-BuPO₃)₄], where R = p-i-PrC₆H₄ (1), p-ClC₆H₄ (2). Further, reaction of organostibonate phosphonate with Ti­(OⁱPr)₄ in the presence of pyridine under solvothermal conditions afforded the mixed-metal titanium stibonate hexanuclear clusters [(RSb)₂Ti₄(μ₃-O)₂(μ₂-O)₂(t-BuPO₃)₄(μ-OCH₃)₄(OCH₃)₄], where R = p-i-PrC₆H₄ (3), p-ClC₆H₄ (4). Band gap measurements were performed on 1–4. They reveal a remarkable reduction in the band gap on moving from the heavier main-group-based oxo cages (1 and 2) to the titanium-incorporated oxo cages (3 and 4).